1. Field of The Invention
The present invention relates to the technological field of sputtering apparatus, and particularly to improvement of step coverage of sputtering apparatus.
2. Description of Related Art
A related sputtering apparatus is shown by numeral 110 in FIG. 6.
This sputtering apparatus 110 has a vacuum chamber 112, with a wafer stage 114 fitted onto a bottom wall of the vacuum chamber 112 in such a manner as to be insulated from the wall surface of the vacuum chamber 112.
A ceiling plate 113 is fitted to the ceiling side (of the vacuum chamber 112 via an insulating member 118. A magnet 119 is located on the ceiling plate 113 via an insulating member (not shown) and a target 120 is located at an inside surface of the vacuum chamber 112 at the surface on the opposite side to the magnet 119.
A cooling equipment 115 and a substrate table 116 are mounted, in order, on the wafer stage 114. A chucking electrode (not shown) is located inside the substrate table 116. The inside of the vacuum chamber 112 is evacuated and a substrate 117 is mounted on the substrate table 116. When a voltage is then applied to the chucking electrode, the substrate 117 is electrostatically chucked to the surface of the substrate table 116.
A sputtering power supply 125 is connected to the target 120 and the vacuum chamber 112 is connected to earth potential. After the inside of the vacuum chamber 112 is evacuated and the substrate 117 is electrostatically chucked onto the substrate table 116, a sputtering gas is introduced into the vacuum chamber 112 and the sputtering power supply 125 is activated. When a negative voltage is then applied to the target 120, a plasma is generated in the vicinity of the surface of the target 120 as a result of electrons being captured by magnetic lines of force of the magnet 119. When this plasma is incident to the target 120, the material making up the target 120 flies off from the surface of the target 120 as sputtering particles.
At the sputtering apparatus 110, a cylindrical deposition preventing plate 111 is located within the vacuum chamber 112 and is fixed to the surface of the inner wall of the vacuum chamber 112. The deposition preventing plate 111 is also positioned at earth potential together with the vacuum chamber 112 because the vacuum chamber 112 is located at earth potential.
A negative voltage is applied to the wafer stage 114, and the substrate 117 is positioned at negative potential. Electrons in the plasma are chucked towards the deposition preventing plate 111, and sputtering particles having a positive potential flying off from the target 120 are chucked towards the substrate 117. As a result, sputtering particles fly off in a direction along a central axis of the deposition preventing plate 111 within the deposition preventing plate 111; and a thin film is formed at the surface of the substrate 117 upon the sputtering particles reaching the surface of the substrate 117.
A water path 123 is provided within the cooling equipment 115. After a thin film is formed to a predetermined thickness at the surface of the substrate 117, cooling water flows in the water path 123. After the substrate 117 is cooled, the substrate 117 is carried outside of the vacuum chamber 112. When an as-yet unprocessed substrate is introduced into the vacuum chamber 112, the thin film forming operation can then be repeated.
The sputtering particles do not become attached to the surface of the inner wall of the vacuum chamber 112 because the deposition preventing plate 111 is located at the periphery of the flight path of the sputtering particles. Therefore, when a multiplicity of substrates 117 are processed and the inside of the vacuum chamber is cleaned, the deposition preventing plate 111 is extracted; and thin film that has become attached to the inner peripheral surface of the deposition preventing plate 111 is cleaned and removed.
Therefore, with the deposition preventing plate 111 of the above configuration, the prevention of thin film becoming attached to the surface of the inner wall of the vacuum chamber 112 is halted when the deposition preventing plate 111 is extracted, and this cannot be said to improve the performance of the sputtering apparatus 110.
In recent years, attempts have been made to improve the step coverage of thin films formed at the surface of the substrate 117 by applying a voltage to the deposition preventing plate 111, but sufficient step coverage has yet to be obtained
As the present invention sets out to resolve the aforementioned problems of the related art, it is the object of the present invention to provide a sputtering apparatus capable of forming a thin film with a good step coverage.
In order to resolve the aforementioned problems, a sputtering apparatus comprises a vacuum chamber, a target positioned within the vacuum chamber, a substrate table located within the vacuum chamber at a position facing the target, an anode electrode surrounding the periphery of a portion, on the target side, of flying space where sputtering particles flying off from the target are flying, of space between the target and the substrate table, and an earth electrode encompassing a portion, of the remaining portion of the flying space, between the anode electrode and the substrate table. The earth electrode and the anode electrode are electrically insulated from each other and are subjected to the application of different voltages.
The sputtering apparatus of the present invention has a power supply, wherein the vacuum chamber and the earth electrodes are connected to earth, and the power supply applies a positive voltage to the anode electrode.
With this sputtering apparatus, a substrate table is mounted on a wafer stage; and a negative voltage can be applied to the wafer stage.
Further, with this sputtering apparatus, the earth electrode can be divided into first and second earth electrodes, with a gap being formed between the first and second earth electrodes.
Moreover, with the sputtering apparatus of the present invention having the target located at the top and the substrate table located below the target, the anode electrode can be formed a tubular shape, and a flange can be provided at the outer periphery of one end of the anode electrode, with a conductive terminal member insulated electrically from the vacuum chamber projecting at the inside of the vacuum chamber, and at the anode electrode, the flange mounting the terminal member, and the opening on the opposite side to the opening provided with the flange facing the substrate table.
Still further, in a thin film manufacturing method of the present invention where a target is positioned in a vacuum chamber, the vacuum chamber is connected to earth potential, a negative voltage is applied to the target so that a plasma is formed in the vicinity of the surface of the target, and sputtering particles flying off from the target reach a substrate positioned with a surface facing the target so as to form a thin film on the surface of the substrate, with an anode electrode surrounding the periphery of a portion, on the target side, of flying space where sputtering particles flying off from the target are flying, of space between the target and the substrate table, comprising a step of connecting the potential of the periphery surrounding the substrate to earth potential, applying a positive voltage to the anode electrode, and sputtering the target.
In the present invention, a negative bias voltage is applied to the substrate.
When the present invention is configured in the above manner, when the space between the target and the substrate is taken to be the flying space of the sputtering particles, the potential of the vacuum chamber is connected to earth potential; and a positive voltage can be applied to the anode electrode encompassing the portion of this flying space which is on the target side. The same earth potential, as applied to the vacuum chamber can then also be applied to the earth electrode encompassing the substrate-side portion of the flying space.
When a large negative voltage is applied to the target and a smaller negative voltage compared to that applied to the target is applied to the substrate, in experiments, the sputtering particles are made to converge onto the substrate and a large number of sputtering particles therefore become incident to the substrate.
This is particularly useful because just a few sputtering particles can also be made to converge onto the substrate when only a few sputtering particles fly off from the target or when only a few sputtering particles fly in the direction of the substrate.
For example, if the target is copper and sputtering gas is introduced just when sputtering commences, after sputtering starts once, when the sputtered copper is again made incident to the target so that the copper is sputtered, self-discharging of the copper itself can be utilized to maintain a plasma. However, the sputtering particles of copper flying on the substrate side are few with sputtering employing the self-discharging of copper; thereby, making the present invention particularly effective.
Further, it is necessary to insulate the anode electrode from the vacuum chamber when a positive voltage is applied to the anode electrode. However, with the sputtering apparatus of the present invention, a terminal member insulated from the vacuum chamber projects at the inner surface of the vacuum chamber, and a flange of the anode electrode is positioned above this terminal member. The anode member therefore does not make contact with the vacuum chamber and can be extracted from the vacuum chamber just as a result of being lifted up, which result in effective and easy maintenance. The above-described objects and other objects, features, and benefits or advantages of the present invention will become more apparent from the following detailed description of embodiments of this invention in conjunction with the accompanying drawings.